Sample investigating system

ABSTRACT

A spectroscopic system for adjusting spacing between an adjacent source/detector as a unit, and a sample, and a reflecting means for directing an incident beam which reflects from said sample back onto said sample and then into the detector along a locus which is in a plane of incidence that is offset from that of the incident beam, or directly from the reflecting means into the detector, including means for reducing reflections of a beam of electromagnetic from the back of a sample, including methodology of use.

This Application Claims Benefit from Provisional Application Ser. No.60/691,297 Filed Jun. 17, 2005; and from Provisional Application Ser.No. 60/790,588 Filed Apr. 10, 2006.

TECHNICAL FIELD

The present invention relates to systems for investigating samples, andmore specifically to a spectroscopic system which comprises means foradjusting spacing between a commonly mounted adjacent source/detectorand a sample, and a reflecting means for directing an incident beamwhich reflects from said sample back onto said sample and then into saiddetector or directly into the detector, along a locus which is in aplane of incidence that is offset from that of the incident beam. Thepresent invention further relates to reduction of reflections of a beamof electromagnetic from the back of a sample upon which it is incidentat an oblique or normal angle, and especially to system and methodologyfor reducing such back reflections from continuously moving samples.

BACKGROUND

It is known to investigate samples with spectroscopic electromagneticradiation. It is also known to place a source and a detector ofelectromagnetic radiation adjacent to one another and use reflectingmeans to direct an electromagnetic beam. For instance, a Patent to He etal., U.S. Pat. No. 5,963,327 describes use of a total internallyreflecting prism to direct an incident beam of electromagnetic radiationprogressing in a horizontally oriented plane into a vertically orientedplane so that it interacts with a sample at an intended angle ofincidence, and then, via a second total internally reflecting prismredirect the reflected beam into the original horizontally orientedplane and into the detector. Said 327 Patent system enables a morecompact arrangement than more conventional geometry systems whichposition source and detector on laterally opposite sides of a sample. Itis also noted that the 327 Patent system positions an aperture at theinput to the detector.

Said 327 Patent system separates the incident and reflected beams bypositioning the total internally reflecting prisms which intercept theincident and reflected beams, (with respect to the sample), at somedistance apart from one another. And, it is noted that two suchreflective means are necessary.

It would be of benefit if a single reflecting means could be utilized ina system which positions source and detector adjacent to one another,and if there was no necessity of changing the locus of the beam into anorthogonally related plane.

It is also known that when a beam of electromagnetic radiation is causedto impinge on the surface of a sample at an oblique or normal angle,reflected electromagnetic radiation from said sample generally containscomponents not only from its surface, but also from the backsidethereof. The effect of said backside reflections can be difficult tomodel, and makes characterization of surface films far more difficult,even essentially impossible. It is therefore desirable to reduce ofeliminate the presence of said backside reflections.

DISCLOSURE OF THE INVENTION

The presently disclosed invention comprises a system for monitoringsamples comprising:

-   -   a source of spectroscopic electromagnetic radiation;    -   a means for supporting a sample;    -   a reflecting means; and    -   a detector of spectroscopic electromagnetic radiation;        Said source and detector are mounted to a common support and        laterally offset from one another such that in use an incident        beam of electromagnetic radiation, from said source thereof, is        caused to, approach a sample placed on said means for supporting        a sample at an intended angle of incidence along a first locus,        reflect from said sample interact with said reflecting means and        proceed along a selection from the group consisting of:    -   again interact with said sample and re-reflect therefrom at the        intended angle of incidence, then proceed along a second locus        and enter said detector; and    -   proceed along a second locus and enter said detector.        Said beam is also caused to pass through an intensity        controlling means either before or after interaction with a        sample.

Where the beam which reflects from said sample interacts with saidreflecting means and again interacts with said sample, re-reflectstherefrom at the intended angle of incidence, and then proceeds along asecond locus and enter said detector, it is noted that said sample istipped in plane of incidence so as to direct said electromagnetic beamwhich re-reflects from said sample at said intended angle of incidence,along said second locus which is offset from said the locus of saidincident beam.

Said presently disclosed invention further comprises means forcontrolling the distance between said source and detector which aremounted to a common support, and said means for supporting a sample.Said means for controlling the distance between said source and detectorwhich are mounted to a common support, and said means for supporting asample can be means for controlling either or both the position of saidcommon support and the position of said means for supporting a sample.

A preferred arrangement provides that both said source of spectroscopicelectromagnetic radiation and detector of spectroscopic electromagneticradiation are mounted in a common enclosure, and that said commonenclosure comprises means for purging volume therewithin with externallyentered air or gas.

The intensity controlling filter means can be selected from the groupconsisting of:

-   -   electronic gain control means in the detector;    -   a neutral density filter; and    -   a low pass filter.        Further, said intensity controlling filter means can comprises a        selection from the group consisting of:    -   at least one element which can be inserted into and removed from        the locus of said incident beam of electromagnetic radiation;        and    -   a rotatable element which is inserted into the pathway of the        locus of said incident beam of electromagnetic radiation, said        rotatable element presenting said incident electromagnetic beam        with different degrees of intensity attenuation at different        rotation amounts.

Said presently disclosed invention can also comprise means for providinga purging flow of gas during data acquisition to least at one selectionfrom the group consisting of:

-   -   said sample; and    -   said reflecting means;

A method of investigating a sample comprising the steps of:

a) providing a system for monitoring samples as described above;

b) causing said distance between said common support and said means forsupporting a sample to be increased and positioning a standard sample onsaid means for supporting a sample, then causing said distance betweensaid common support and said means for supporting a sample to bedecreased;

c) causing an incident beam of electromagnetic radiation from saidsource thereof to pass through said intensity controlling means,approach a sample placed on said means for supporting a sample at anintended angle of incidence along a first locus, reflect from saidsample, interact with said reflecting means, then, after optionallyagain interacting with said sample, proceed along a second locus andenter said detector;

d) adjusting said intensity controlling filter means such that saiddetector provides a non-saturated signal;

e) causing said common support and said means for supporting a sample tobe increased and positioning a test sample on said means for supportinga sample, then causing said distance between said common support andsaid means for supporting a sample to be decreased;

f) adjusting said intensity controlling filter means such that saiddetector provides a non-saturated signal; and

g) analyzing data provided by detector.

The present invention further provides an approach to investigation ofsamples which reduces the effect of back reflections. A system foraccomplishing this provides:

-   -   a sample;    -   a means for supporting a sample;    -   a source of a beam of electromagnetic radiation; and    -   a detector of said beam of electromagnetic radiation;        wherein said means for supporting a sample is present directly        under said sample at the location thereof whereat, during use, a        beam of electromagnetic radiation provided by said source        thereof is caused to impinge thereupon at an oblique or normal        angle of incidence. Said means for supporting a sample and said        sample can be characterized by a selection from the group        consisting of:    -   having essentially matched indices of refraction; and    -   having liquid present at the interface therebetween which is        essentially index essentially matched to that of said sample.        Said sample and said means for supporting a sample can be        variously rigid or flexible, and an important application of the        present invention system is where relative motion therebetween        is continuous. This can occur, for instance, where the sample is        a ribbon or sheet which is continuously pulled over the means        for supporting a sample. In such a case, said means for        supporting a sample can be a roller characterized by a selection        from the group consisting of:    -   it is rigid; and    -   it is deformable.        For instance, where a sample is rigid, benefit derives from        using a deformable means for supporting a sample in order to        facilitate effecting a good contact therebetween. This point is        less important, though not irrelevant however, where the sample        is flexible and can conform to the shape of said means for        supporting a sample, and/or in the case where liquid is caused        to be present between said sample and said means for supporting        a sample.

It is noted that index matching need not be perfect to achievebeneficial results.

The present invention will be better understood by reference to theDetailed description Section of this Application, in combination withthe Drawings.

SUMMARY OF THE INVENTION

It is therefore a purpose and/or objective of the present invention toprovide a spectroscopic system which comprises:

-   -   means for adjusting spacing between an adjacent source/detector        as a unit, and a sample; and    -   a reflecting means for directing an incident beam from the        source which reflects from said sample back onto said sample and        then into the detector along a locus which is in a plane of        incidence that is offset from that of the incident beam, or        which directs an incident beam from the source directly from the        reflecting means into the detector.    -   wherein said means for supporting a sample is present directly        under said sample at the location thereof whereat, during use, a        beam of electromagnetic radiation provided by said source        thereof is caused to impinge thereupon at an oblique or normal        angle of incidence;

It is another purpose and/or objective of the present invention to applythe system of the present invention to investigate a sample which issupported by a means for supporting a sample, said sample and means forsupporting it being characterized by a selection from the groupconsisting of:

-   -   they have matched indices of refraction; and    -   the have liquid present at the interface therebetween which is        essentially index matched to that of said sample.

Other purposes and/or objectives of the present invention will becomeapparent by a reading of the Specification and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a preferred embodiment of the system of the presentlydisclosed invention.

FIG. 2 shows a modified embodiment of the system of the presentlydisclosed invention.

FIGS. 3 and 4 show that means for enabling relative motion ofsource/detector and sample/reflecting means can be employed in thesystem of the disclosed invention.

FIGS. 5-8 demonstrate samples which can be investigated by the presentinvention system, including means to reduce back side reflections.

DETAILED DESCRIPTION

Turning now to FIG. 1, there is shown a Source (S) and Detector (D) in aCommon Enclosure (CE), a Sample (SM) and a Reflective Means (RM). Notethat an Incident Beam (IB) is shown impinging on said Sample (SM) alongone locus, reflecting therefrom, interacting with the Reflecting Means(RM), again reflecting from said Sample (SM) and proceeding along asecond locus to said Detector (D) along a second locus. Note that theSecond Locus of the Reflected Beam (RB) is effected by a set rotation ofthe Sample (SM) about the axis identified by (POI), such that the entryto Detector (D) for the Reflected Beam (RM) is offset, above or below,the Source (S) of said Incident Beam (IB).

FIG. 2 shows a variation of the presently disclosed invention system.Note that the Reflecting Means (RM) is oriented not to direct theIncident Beam (IB) which reflects from the Sample (SM) back onto theSample (SM), but rather directly toward the Detector (D) as Beam (RB).In this configuration there is no requirement that the plane ofincidence of the sample be rotated, as demonstrated in the FIG. 1configuration by (POI), although it, of course, could be so rotated.

Both FIGS. 1 and 2 show the presence of an intensity controlling means(FM) which is present to condition the intensity of the electromagneticbeam. This is to avoid saturation of the Detector electronics. Note thatthe intensity control means (FM′) could be present on the Detector (D)side.

Note in both FIGS. 1 and 2, the optional presence of Purging gas flowmeans (PI) and (PO). Flowing a gas can serve to cool and to provide anon-absorbing ambient for IR and UV wavelengths, for instance, in theCommon Enclosure (CE). Likewise note the optional presence of means forpurging the Sample (SM) and/or Reflecting Means (RM).

FIGS. 3 and 4 indicate that the adjacent Source (S) and Detector (D) asa unit and/or the Sample (SM) and Reflecting Means (RM) as a unit can bemounted to allow relative motion therebetween. This can be useful whenit is necessary to mount different samples, for instance, a standardsample followed by a test sample.

Continuing, FIGS. 5-8 demonstrate samples (SM) which can be investigatedby the present invention system, including means to reduce back sidereflections. As disclosed in the foregoing, the system generallycomprises a Source (S) and Detector (D) as a unit, and a Sample (SM).The system in FIGS. 5-8 is further show that:

-   -   said sample (SM) has top (S1) and bottom (S2) surfaces; there is        a means for supporting (R) said sample (SM) having an outer        surface (S3); and    -   said source (PSG) is shown as a polarization state generator of        a beam of electromagnetic radiation (EMI) and said detector        (PSD) is shown as being a polarization state detector and as        receiving of a reflected beam of electromagnetic radiation        (EMR).        Importantly, note that a portion of the beam (EMI) transmits        into the sample as (EMT), and can reflect from an interface        between said sample (SM) and said means for supporting (R) said        Sample (SM). Said means for supporting (R) a sample (SM) is        present under said sample (SM) at the location thereof whereat,        during use, a beam of electromagnetic radiation (EMI) provided        by said source thereof is caused to impinge thereupon at an        oblique or normal angle of incidence. Also note that said means        for supporting (R) a sample (SM) and said sample (SM) are        characterized by a selection from the group consisting of:    -   having matched indices of refraction (FIGS. 5 and 6); and    -   having liquid (L) present at the interface therebetween which is        essentially index matched to that of said sample (SM).        Said means for supporting (R) and said sample (SM) can each be        rigid or deformable.

A method of monitoring reflections of electromagnetic radiation causedto impinge on the surface of a sample (SM) at an oblique or normal angleof incidence, while substantially preventing backside reflectionstherefrom from complicating the results, comprising the steps of:

a) providing a system comprising:

-   -   a sample (SM);    -   a means for supporting (R) a sample (SM);    -   a source (PSG) of a beam (EMI) of electromagnetic radiation; and    -   a detector (PSD) of said beam (EMR) of electromagnetic        radiation;        wherein said means for supporting (R) a sample (SM) is present        directly under said sample (SM) at the location thereof whereat,        during use, a beam (EMI) of electromagnetic radiation provided        by said source (PSG) thereof is caused to impinge thereupon at        an oblique or normal angle of incidence;        said means for supporting (R) a sample and said sample being        characterized by a selection from the group consisting of:    -   having matched indices of refraction; and    -   having liquid (L) present at the interface therebetween which is        essentially index essentially matched to that of said sample        (SM);

b) causing said source (PSG) of a beam of electromagnetic radiation toprovide a beam (EMI) of electromagnetic radiation to impinge on asurface of said sample (SM), at an oblique or normal angle of incidence;

c) monitoring electromagnetic radiation reflected (EMR) from said sample(SM) surface which enters said detector (PSD).

It is also to be understood that the (PSG) and (PSD) in FIGS. 5 and 6can be rotated in position about a normal to the sample (SM) through0-360 degrees so that the plane formed thereby is oriented as shown, orin any such rotated position.

Having hereby disclosed the subject matter of the present invention, itshould be obvious that many modifications, substitutions, and variationsof the present invention are possible in view of the teachings. It istherefore to be understood that the invention may be practiced otherthan as specifically described, and should be limited in its breadth andscope only by the Claims.

1. A system for monitoring samples comprising: a source of spectroscopicelectromagnetic radiation; a means for supporting a sample; a reflectingmeans; a detector of spectroscopic electromagnetic radiation; and anintensity controlling filter means; said source and detector beingmounted to a common support and laterally offset from one another, suchthat in use an incident beam of electromagnetic radiation from saidsource thereof is caused to approach a sample placed on said means forsupporting a sample at an intended angle of incidence along a firstlocus, reflect from said sample, interact with said reflecting means andproceed along a selection from the group consisting of: again interactwith said sample and re-reflect therefrom at the intended angle ofincidence, then proceed along a second locus and enter said detector;and proceed along a second locus and enter said detector; said beam alsobeing optionally caused to pass through said intensity controllingmeans.
 2. A system as in claim 1, in which the beam which reflects fromsaid sample interacts with said reflecting means and again interactswith said sample, re-reflects therefrom at the intended angle ofincidence, and then proceeds along a second locus and enter saiddetector; wherein said sample is tipped in plane of incidence so as todirect said electromagnetic beam which re-reflects from said sample atsaid intended angle of incidence, along said second locus which isoffset from said the locus of said incident beam.
 3. A system as inclaim 1 in which said source of spectroscopic electromagnetic radiationand detector of spectroscopic electromagnetic radiation are mounted in acommon enclosure.
 4. A system as in claim 1 in which said sample andreflecting means are present in a common enclosure which comprises meansfor purging volume therewithin with externally entered air or gas.
 5. Asystem as in claim 1, in which said intensity controlling filter meansis selected from the group consisting of: a neutral density filter; anda low pass filter.
 6. A system as in claim 1 in which at least oneselection from the group consisting of: said sample; and said reflectingmeans; are purged with a flow of gas during data acquisition.
 7. Asystem as in claim 1, in which said intensity controlling filter meanscomprises a selection from the group consisting of: at least one elementwhich can be inserted into and removed from the locus of said incidentbeam of electromagnetic radiation; and a rotatable element which isinserted into the pathway of the locus of said incident beam ofelectromagnetic radiation, said rotatable element presenting saidincident electromagnetic beam with different degrees of intensityattenuation at different rotation amounts.
 8. A system as in claim 1, inwhich said sample and said means for supporting a sample have matchedindices of refraction.
 9. A system as in claim 1, in which there ispresent between said sample and said means for supporting a sample aliquid having an index of refraction matching that of said sample.
 10. Asystem as in claim 1, in which the incident beam, after reflecting fromsaid reflecting means proceeds to again interact with said sample andre-reflect therefrom at the intended angle of incidence, then proceedalong a second locus and enter said detector.
 11. A system as in claim1, in which the incident beam, after reflecting from said reflectingmeans proceeds along a second locus and enter said detector.